A brush of the generic type is known for instance from DE 31 28 749 A1. This publication also describes the problem that any direct contact of the metal wire sections with paradontous tooth-necks or fillings and bridges may generate painful galvanic effects.
For the solution of this problem, in the known interdental toothbrush provision is made for the wire sections of steel wire to be surrounded by an electrically insulating layer, which may consist of a flexible and non-abrasive material such as for instance nylon or polyurethane. It is provided that this layer can be applied as a varnishing by dipping or spraying or that it coats the wire in the form of a hose.
If such a coating is to be applied as such after the manufacture of the brush, this is only feasible with comparatively expensive manufacturing techniques and the individual bristles must moreover have a comparatively large distance one from the other. If, prior to being twisted, the wire is provided or coated with the plastic layer, then there is the risk that the layer cracks as a result of the twisting and also the engagement of the wire with the fiber portions is affected by the plastic coating, so that it is not possible, at least not without any difficulties, to produce the desired distribution of the tips. Moreover, such a coating will inevitably increase the effective thickness of the twisted central portion of the brush, so that the brush can no longer enter into narrow tooth gaps to the extent desired.